1. Field of the Invention
The present invention relates to an optical disk apparatus which reproduces information from an optical disk such as a DVD or a CD set to a main unit thereof.
2. Description of the Related Art
In an optical disk apparatus which reproduces information from an optical disk such as a DVD or a CD, conventionally, equalizer adjustment is applied on an RF signal (an RF signal output from a pickup head) which is read out from an optical disk set to a main unit. As well known in the art, an RF signal which is read out from an optical disk contains various frequency components, and the level of the signal is lower as the frequency is higher. As the level of the signal is lower, jitter is worse. Equalizer adjustment is a process for optimizing jitter of an RF signal, and more specifically a process in which, with respect to an RF signal read out from an optical disk, components higher than a certain frequency are cut off, and boosting is performed.
The cutoff frequency (Fc) of an RF signal and the boost amount (Bt) which are used in equalizer adjustment are varied depending on the data recording density, the signal quality, and the like in an optical disk to be reproduced (an optical disk set to the main unit of the optical disk apparatus), and hence must be set in accordance with the optical disk set to the main unit. In a conventional optical disk apparatus, therefore, the cutoff frequency (Fc) of an RF signal and the boost amount (Bt) by which jitter is optimized are detected for the optical disk set to the main unit prior to the reproduction process (see Patent References 1, 2). In the reproduction process, equalizer adjustment is performed on the basis of the cutoff frequency (Fc) and the boost amount (Bt) which are detected as described above.
Particularly, in JP-A-2001-126261, there is disklosed a configuration in which, in order to optimize jitter in accordance with the reproduction position (the inner peripheral side or the outer peripheral side) of an optical disk, the cutoff frequency (Fc) of an RF signal and the boost amount (Bt) are changed in accordance with the reproduction position of the optical disk. In JP-A-2002-008243, there is disklosed a configuration in which a process of detecting the cutoff frequency (Fc) of an RF signal and the boost amount (Bt) is simplified and the time period of the process is shortened.
In a conventional optical disk apparatus, the RF signal cutoff frequency (Fc) and the boost amount (Bt) for optimizing jitter are detected under the state where an optical disk set to a main unit is rotated at a speed for a reproduction process (the predetermined rotational speed in the invention). Specifically, when the user applies an input operation for starting the process of reproducing the optical disk on the main unit, the optical disk set to the main unit starts to be rotated, and, after the rotational speed of the optical disk reaches the rotational speed for the reproduction process, the RF signal cutoff frequency (Fc) and the boost amount (Bt) are detected.
As described above, a conventional optical disk apparatus is configured so that, after the rotational speed of the optical disk reaches the rotational speed for the reproduction process, the RF signal cutoff frequency (Fc) and the boost amount (Bt) are detected. Consequently, there is a waiting time between the start of the rotation of the optical disk and the timing when the rotational speed of the optical disk reaches the rotational speed for the reproduction process. Because of the waiting time, the time between the timing when the user conducts an input operation for starting reproduction, and that when reproduction of the optical disk is actually started, i.e., the time for which the user must wait is prolonged, thereby causing a problem in that the usability of such an apparatus is poor.